The invention relates to methods of diagnosing the presence, type, or severity of a dementia.
Alzheimer""s disease (xe2x80x9cADxe2x80x9d) is a degenerative brain disorder that afflicts millions of people worldwide. It is the most common form of dementia and can affect memory, mood, personality, and cognitive ability. The risk of developing AD becomes greater with age. As the average human life-span continues to increase, the number of people developing AD at some point in their lives is escalating rapidly. Currently, an estimated 1 in 20 people over the age of 65 are affected by some form of dementia. In persons over the age of 80, that number rises to 1 in 5.
The effects of AD can be devastating. Early symptoms include forgetfulness, learning difficulties, and loss of concentration. The later stages of the disease are characterized by disorientation, extreme memory loss, impairment of speech and reading comprehension, and changes in personality. Dramatic mood swings can occur, including outbursts of anger, bouts of fearfulness, and periods of deep apathy or depression. The sufferer becomes increasingly confused, particularly when confronted with unfamiliar settings, and may wander off and become lost. Physical problems, such as an odd gait, a loss of coordination, an inability to chew and swallow, and an inability to control bowel and bladder functions, gradually develop. Eventually, the patient may become totally noncommunicative, physically helpless, and incontinent. The disease is invariably fatal.
AD can also have a profound impact on the relatives of the person suffering from the disease. About seventy percent of AD patients are cared for at home by family members. In the early and middle stages of AD, patients may need help in managing their financial and business affairs. As the disease progresses, the affected person becomes steadily more dependent on caregivers to help perform daily tasks. The patient""s mental functioning eventually deteriorates to the point where it is not safe to leave the person unattended. Ultimately, the disease may leave its victims bedridden and unable to care for themselves. Under these circumstances, AD can take a tremendous physical, financial, and emotional toll on the caregivers.
Although there is currently no cure for AD, early diagnosis is important for a number of reasons. For instance, it is crucial to rule out other conditions which have symptoms that are similar to AD, but which are treatable. In addition, the patient and family members can receive much help and advice from doctors and other professionals in coping with this disease. Furthermore, medications are available which can help relieve some of the common symptoms of AD, including depression, anxiety, and sleep disturbance. There is also hope that treatments may be developed in the future which will slow or halt the progression of the disease, making early detection and intervention even more vital.
Diagnosing AD can often be difficult, especially in the early stages, because many of the symptoms of the disease mirror the natural signs of aging. In some situations, a definitive diagnosis may not be possible until the patient has died and an autopsy can be performed. There are also several forms of dementia that appear superficially similar to AD, but have distinct underlying pathological processes. These dementias are often indistinguishable from AD using conventional testing techniques.
Current psychological tests for AD that are used clinically focus on deteriorations in memory, particularly in short-term or xe2x80x9cworkingxe2x80x9d memory. In general, the disorder must be fairly well advanced before significant impairments in memory are observed. Consequently, these tests are not fully capable of diagnosing AD in the early stages. Thus, there is a need for an easily administered, non-invasive, and reliable test for detecting AD while still in the early stages of development.
The regions of the brain that mediate working memory also regulate the capacity for sustained attention (i.e., vigilance), control of impulses, and motor activity. We believe that, in patients suffering from AD and other dementias, impairment of these functions often occurs prior to detectable changes in memory. We posit that testing a patient for disturbances in attention, impulsiveness, and/or motor function can lead to early diagnosis of AD and other forms of dementia. Earlier diagnosis, in turn, makes it possible to begin treating the underlying disorder while still in the early stages, in order to halt or slow its progression.
Accordingly, the present invention provides a method of diagnosing the presence, type, or severity of a dementia in a human subject using computerized testing, which method includes the steps of: (a) placing, in proximity to the subject, a monitor that is connected to a computer, and a device that is controllable by the subject and that is also connected to the computer; (b) presenting the subject with instructions for activating the device in response to visual images on the monitor; (c) presenting to the subject one or more visual images on the monitor; (d) storing in the computer the instances of device activation by the subject; and (e) scoring the accuracy or response time, or both, of device activation, wherein scoring below a pre-determined level is diagnostic for dementia. Alternatively, more complex measures of subject response patterns may be analyzed.
In one embodiment of the invention, the method further includes the steps of: (f) using a motion analysis device connected to the computer to record the movements of the subject during presentation of the visual images; (g) storing the record of these movements in the computer; (h) analyzing the recorded movements for deviations from pre-determined norms; and (i) using the analysis of step (h) together with the scoring of step (e) in diagnosing dementia. The motion analysis device is preferably an infrared camera capable of detecting small infrared reflective markers. These markers can be placed at various positions on the subject, such as the head, elbow, and shoulders, in order to monitor the movements of these portions of the subject""s body.
The method of the invention can be used to diagnose and distinguish various forms of dementia, including dementia associated with Alzheimer""s disease, frontotemporal degenerative dementias (e.g., Pick""s disease, corticobasal ganglionic degenerations, and frontotemporal dementia), Huntington""s disease, Creutzfeldt Jakob disease, Parkinson""s disease, cerebrovascular disease, head trauma, and substance abuse).
Other features and advantages of the invention will be apparent from the following detailed description and from the claims.